Wiring error detector for door operator

Abstract

A door operation control system has a door opening for moving a door between open and closed positions. A door operator control circuit selectively operates the drive means to move the door between the open and closed positions. An obstruction detection device detects whether there is an obstruction in the path of the door between the open and closed positions and generates a signal in response thereto. The obstruction detection device is connected to the control circuit by wiring to permit operation of the door opener in the absence of a signal from the obstruction detection device and to prevent certain operations of the door opener in the presence of a signal from the obstruction detection device. An error detection circuit detects faults or errors in the wiring and generates a signal to prevent certain operations of the door operator when the faults or errors are detected. The error detection circuit prevents unsafe operation of the door opener if a wiring error has made the obstruction detection device inoperative.

What is claimed is: 
     
       1. A door operator system comprising: a door opener for opening and closing a door across a doorway;   a control circuit for operating the door opener, the control circuit having an input for receiving a first signal indicating the presence of an obstruction in the doorway and a second signal indicating the absence of an obstruction in the doorway;   an obstruction detection means for sensing obstructions in the doorway, the obstruction detection means having an output for sending a third signal indicating the presence of an obstruction and a fourth signal indicating the absence of an obstruction;   an error detector circuit connected between the control circuit and the obstruction detection means, the error detector circuit providing the first signal on the control circuit input when the third signal is received on the obstruction detection means output, the error detector circuit providing the second signal on the control circuit input when the fourth signal is received on the obstruction detection means output, the error detector circuit and the obstruction detection means providing a splitter circuit connected to the output of the obstruction detection means for maintaining the fourth signal on the obstruction detection means output within a predetermined range of signals during normal operation of the obstruction detection means, the error detector circuit including a signal sensing circuit for sensing if the signal received on the obstruction detection means output is outside the predetermined range and for providing a first signal on the control circuit input when the signal on the obstruction detection means output is outside the predetermined range, whereby a short circuit or an open circuit in the obstruction detection means output results in the first signal on the control circuit input.   
     
     
       2. The door operator system as defined in claim 1, wherein the third signal comprises a first voltage level, and the fourth signal comprises a second voltage level, and wherein the signal sensing circuit comprises a voltage level detector for detecting whether the voltage on the obstruction detection means output is above or below a predetermined range of voltages. 
     
     
       3. The door operator system as defined in claim 1, wherein the control circuit and the obstruction detection means are also connected to a reference signal, the reference signal being outside the predetermined range of signals. 
     
     
       4. The door operator system as defined in claim 3, wherein the reference signal comprises a ground, the third signal comprises a first voltage level substantially spaced from the ground level, and the fourth signal comprises a second voltage level substantially spaced from the ground level, the first and second voltage levels being within a predetermined voltage range, the ground level being outside the predetermined voltage range, the signal sensing circuit detecting whether the voltage on the obstruction detection means output is above or below a predetermined range of voltages, whereby the signal sensing circuit detects a ground level voltage signal on the obstruction detection means output. 
     
     
       5. The door operator system as defined in claim 1, wherein the control circuit is also connected to a supply signal, the supply signal being outside the predetermined range of signals. 
     
     
       6. The door operator system as defined in claim 5, wherein the supply signal comprises a supply voltage level, the third signal comprises a first voltage level substantially spaced from the supply voltage level, and the fourth signal comprises a second voltage level substantially spaced from the supply voltage level, the first and second voltage levels being within a predetermined voltage range, the supply voltage level being outside the predetermined voltage range, the signal sensing circuit detecting whether the voltage on the obstruction detection means output is above or below a predetermined range of voltages, whereby the signal sensing circuit detects a short on the obstruction detection means output between the obstruction detection means output and the supply voltage level. 
     
     
       7. The door operator system as defined in claim 1, wherein the control circuit in response to the first signal at the input operates the door opener to open the door if the door is closing and operates the door to remain open if the door is open. 
     
     
       8. The door operator system as defined in claim 1, wherein the control circuit alters operation of the door opener in response to the first signal at the input. 
     
     
       9. The door operator system as defined in claim 8, wherein the control circuit alters operation of the door if the door is closing by stopping the closing of the door and by reversing the movement of the door.